Why after all the upgrades I’ve done to my predator 212 does it only hit 45mph?

Mini Bike & Go-Kart Parts

My apologies for any silly questions, I’m still in the learning process of working on/modifying small engines. I have swapped the springs for 18lb springs, governor is bypassed(ARC billet rod and flywheel will be here in a couple days)
Performance air filter/re jet, straight pipe exhaust, and I believe I’ve got the valves set to the correct space.. Is it because I do not I have a billet ride and fly wheel installed that it’s not going as fast as it could be because it’s typing out at the rpm that these engines top out at? Do you suggest I slap on a torque converter? Maybe I need some larger diameter tires? Just trying to gain some knowledge in the MPH department LOL
Your answer is most likely gearing related. Once you install your billet parts, get yourself a tachometer and see what RPM your engine is turning at WOT. Then you can use that information as a baseline to adjust the gear ratio for top speed. Don’t forget that wheel/tire size is going to affect this, as well as the weight of the bike and rider.
Not sure how fast you are trying to go, but using a centrifugal clutch is always a trade off.
If you gear the bike for top speed, it will be a dog down low and from a stop. If you are only concerned about top speed, than you can keep your clutch and just accept sacrificing low end performance for the top end gain.
But if you want power down low, as well as up top then a torque converter might your best bet.
Just my two cents